Method of knitting fabrics without permanent deformation



April 18, 1967 G. GROEBLI 3,314,123

METHOD OF KNITTING FABRICS WITHOUT PERMANENT DEFORMATION Filed Dec. 9,1963 2 Sheets-Sheet 1.

G. GROEBLI 3,314,123 METHOD OF KNITTING FABRICS WITHOUT PERMANENTDEF'ORMATION April 18, 1967 2 Sheet$-Sheet 2 Filed D60. 9, 1963 UnitedStates Patent 3,314,123 METHOD OF KNITTING FABRICS WITHOUT PERMANENTDEFORMATION Gustave Groebli, Saint-Quentin, France, assiguor to SocieteAnonyme le Textile Delcer, Saint-Quentin, France, a French society FiledDec. 9, 1963, Ser. No. 329,939 Claims priority, application France, Dec.8, 1962, 918,016; Nov. 29, 1963, 955,437 2 Claims. (Cl. 28-72) Thepresent invention rel-ates to knitted fabrics having improved propertiesas regard permanent deformations (here called pouchin-g). Knittedfabrics in accordance with the invention have inextensibility aspectsand characteristics similar to those of fabrics made on weaving looms,but keep the advantages and qualities of knitted fabrics; such knittedfabrics may be supple, if required, and are lower in cost than wovenfabrics.

The principle, when using a warp knit and Raschel loom, consisting ofinserting unknitted straight filling threads between the columns of thestitches, is known. The fabrics thus produced, regarding aspect, lookedlike woven fabrics, but no real use of such fabrics has been made,except for their use as curtain or drape fabrics. Curtain fabrics, whichmerely hang and are decorative, do not require any characteristicsneeded for fabrics employed for tailor-made clothes and the like.

In fact, the essential characteristic of a fabric for clothes, for seatcovers and the like, is the lack of permanent deformation commonlycalled pouching. Pouching is a characteristic of hitherto known knittedfabrics.

The inventor has found that, to suppress all permanent deformation orpoaching, it was necessary that:

(l) The fabric should be completely inextensible or, at least, that allpermanent or elastic lengthening be suppressed, at least in the warpwisedirection of the fabric.

(2) There should be no possible slipping of the threads working as weftthreads with regard to unknitted straight threads working as warpthreads. (In order to overcome such tendency, it is enough to draw upthe cloth warpwise in pinching only the columns of stitches.)

The present invention relates to a knitting method that takes the aboveinto consideration, and that allows the production of a knitted fabricwithout permanent deformation.

This process in which unknitted filling threads are inserted between thecolumns of stitches, is characterized by the use, for the columns ofstitches, of a chain-stitch thread having the property of being morehighly retracted than the filling threads; this chain-stitch thread isable to be fixed or set, after retractation, by thermo-setting, forinstance.

It is necessary in accordance with the invention that the initial lengthof the chain-stitch thread used during the knitting be nearly equal tothe theoretical length in order to obtain inextensible columns ofstitches after the retractation treatment of the fabric.

For all purposes, the stitch cycle is repeated to form the bindingcombination, the chain-stitch thread having a minimum length warpwise orlongitudinally of the fabrics. The process according to the inventioncan be used for many binding combinations types, mainly for those inwhich a chain-stitch thread operates between several columns ofstitches; in this case the chain stitch thread works as a weft thread.The chain stitches do not have any deformation capacity by lengtheningafter the retractation treatment, since the curve of the stitches iscompletely resorbed by such treatment. The columns of stitches havechanged, after retractation, in a complex comparable to a three endstwist that, gathered to the Weft threads and to the filling threads,creates a fabric which presents practically woven fabricscharacteristics.

The invention will be more readily understood and several othercharacteristics as well as advantages will appear after consideration ofmethods decribed in the attached figures.

FIGURE 1 is a knitted fabric according to the invention process beforeretractation treatment.

FIGURE 2 is a view of the fabric shown on FIGURE 1 after retractationtreatment.

FIGURE 3 is a View of other fabric made according to the invention.

In FIGURE 1 there is shown a fabric which includes on one side a row ofchain-stitch threads 1 making columns of stitches or wales and weftthreads 2 and 3 which are operative on the right and left of thechain-stitch threads 1 and link therewith to form stitches in amarquisette pattern. On the other side the fabric is provided withfilling or reinforcing yarns 4 inserted without knitting in a paralleldirection between the columns of stitches. To simplify the figure thereis shown only one filling 3 thread between two columns of stitches, butit will be obviousthat, as a rule, such a filling thread is put betweentwo columns of consecutive stitches. As well, in each column of stitchesthere are weft threads such as those designed by 2 and 3 linked witheach Wale, but here again there is only one thread for each of the twogroups located the first one before and the other one behind the fillingthreads.

In order that this cloth does not pouch it is necessary:

On one side that the traction efforts be supported by threads 4 whichare inextensible (except. for natural elasticity of the threads) as theyare straight and without undulations.

On the other side that the column of stitches 1 that maintain thewaft-like threads 2 and 3 in their loops must not be allowed to bestretched beyond the elastic limit of the chain-stitch yarn, for if anysuch stretch were to occur, the yarns 2, 3 would slide, with no chanceof being returned to their correct position, upon the yarns 4.

. But the technician knows that this last condition cannot be realizedon a knitting machine as it is nearly impossible to realize achain-stitch having. no mechanical lengthening due to:

(a) Necessity of using a chain stitch thread length much longer thancorresponding length of this chain stitch itself (regarding theundulations).

(b) The round shape of a stitch.

(c) Flexibility (or live handle) of any textile thread.

According to the invention to satisfy this condition, there is used forthe columns stitches, a thread 1 having a higher shrinkage than that ofthe filling yarns 4 and being, besides, able to be fixed up in itsshrunk position. We can use a thermo-set thread like a polyamide orpolyester. It is also necessary that the delivered length of thread 1 bein a judicious ratio with corresponding length of thread 4. duringknitting to make the repeat of the binding combination must be such thatafter retractation the retracted length A A' (FIGURE v2) of thread 1 ofthe same repeat corresponding to this of an inextensible stitch, that isto say, showing no empty space allowing elongation.

After knitting, the fabric is put through a shrinkage treatment at thesetting temperature of molecules of thread 1, this treatment being madewith the fabric maintained under a desired tension in order that finallength of this cloth be equal to the delivered length of the fillingyarns 4, but under consideration of the retractation of these fillingthreads. This latter retractation is very limited, only a few percent.

If for instnace 53 meters of filling yarn layers to knit 50 meters ofcloth, the maintained tension during the In fact, length AA of thread 1used treatment will be such that the final length of the piece of clothwill be 53 meters. However, if the filling yarns presented a 2%shrinkage, the tension during treatment would be such as the finallength of the piece of cloth is 52 meters.

In FIGURE 2 we see that after shrinkage the stitches of the variousdiflferent columns or wales are completely lengthened, each column beingcomparable to a three ply yarn. Unlike FIGURE 1, in FIGURE 2 we havebeen able to show several filling yarns 4, each of them being arrangedbetween two columns or wales of stitches.

The length AA of thread 1 that is required in the column or wale ofstitches, must agree nearly precisely with length BB of straight thread4. Accordingly, after many experiments applicant has devised a formulafor determining the choice of yarns to be used in dependence upon theknitting possibilities of a particular kind of loom. In theseexperiments, some of the factors varied were the characteristics of theyarns used and the number of stitches per centimeter of fabric length.

This formula that can be applied in the case of a chainstitch thread isused for only one column of stitches, gives the ratio X of the supply ofchain-stitch thread 1 used in the column of stitches to the supply ofthe filling yarn 4;

in which:

D=density of chain-stitch thread that works in the column of stitches,

N =metric number of this same thread when knitting,

R=shrinkage of the chain-stitch thread relative to the filling yarns,that is to say the complement to unity of the difference between theshrinkage of the chain-stitch thread and of the filling yarn,

M=number of stitches required per unit length of shrunk fabric.

Of course, the technician is obliged to make a judicious choice of yarnswith special characteristics to obtain a ratio X intermediary betweenthe two limits corresponding to a reasonable running of the knittingmachine at his disposal. In certain cases We also can look for threadscorresponding to a predetermined ratio X.

The above-mentoned formula has a precision corresponding to that of itselements and in particular the (relative shrinkage) which may vary withthe yarns used.

So, for instance, variations of R of more or less than 10% from a lot ofthreads to another one, can be absorbed in most of the cases by theelastic-lengthening of these threads.

If R were taken as constant, a departure of 110% from the value of Xfound by calculation would be allowable without departing from the scopeof the invention, for the yarns always have some elasticity which can berelied on to absorb slight differences due to an approximate calculationof chain-stitch yarn delivery.

We have, moreover, studied the case where chain-stitch yarns areoperative between several columns of stitches. We have presented inFIGURE 3 a binding combination in which the chain-stitch thread isoperative between two columns or wales of stitches M and M separated bya wale of the stitches M this chain-stitch yarn 5 acting then as a weftthread. (We must note therefore, that we can provide other weft threadswithout knitting such as threads 3). It is then necessary to add toratio X above-mentioned a correction term X corresponding to asupplementary weft running of thread 5 and given by the followingapproximate formula:

in which letters R, M have the s me meanings as a and n=number ofcolumns of stitches separating the two wales between which thechain-stitch thread is operative,

J gauge of used knitting machine in needle number per an English inch.

Therefore, it is possible to generalize the application of the processaccording to the invention to all binding combinations that can be usedto obtain such cloths.

After thermo-setting the fabric stays as it is. Any stretch left is onlydue to the natural elasticity of the components, which balance therelative inexact factor R.

The formula may lead to the fabric as knitted having relativelycorrugated yarns 4, but these disappear after shrinkage, since shrinkageconverts the wales 1 into complexs which are of similar appearance totwisted yarns without mechanical elongation and which subsequentlybehave like the yarn 4; indeed, the latter can be a twisted yarn and istherefore straight.

I claim:

1. A method of producing knitted fabrics having a repetitive pattern andhaving the appearance and properties of woven fabrics, comprisingfeeding a first yarn which can be shrunk and which can be set afterbeing shrunk and forming rows of stitches therefrom, assembling saidrows of stitches by means of two yarns which act as weft yarns and joinat least two rows of stitches, feeding straight yarn, which shrinks lessthan the first yarn and inserting such straight yarn in unknittedcondition between the rows of stitches, controlling the rate of feedingof the first yarn relative to the rate of feeding of the straight yarnso that the first yarn has a length which markedly exceeds the length ofthe straight yarn and which is substantially equal to the theoreticallength of the first yarn which is required to obtain an inextensible rowof stitches after the shrinkage treatment, subjecting said fabric to ashrinkage treatment, and during the shrinkage treatment maintaining thelength of the fabric substantially equal to the length of the straightfilling yarn after allowing for any shrinkage of the filling yarn.

2. A method of producing knitted fabrics having a repetitive pattern andhaving the appearance and properties of woven fabrics, comprisingfeeding a first yarn which can be shrunk and which can be set afterbeing shrunk and forming rows of stitches therefrom, assembling saidrows of stitches by means of two yarns which act as weft yarns and joinat least two rows of stitches, feeding straight yarn, which shrinks lessthan the first yarn and inserting such straight yarn in unknittedcondition between the rows of stitches, controlling the rate of feedingof the first yarn relative to the rate of feeding of the straight yarnso that the first yarn has a length which markedly exceeds the length ofthe straight yarn and which is substantially equal to the theoreticallength of the first yarn which is required to obtain an inextensible rowof stitches after the shrinkage treatment, and subjecting said fabric toa shrinkage treatment, and during the shrinkage treatment maintainingthe length of the fabric substantially equal to the length of thestraight filling yarn after allowing for any shrinkage of the fillingyarn, the ratio X of the delivery of the yarn used to form a single rowof stitches to the delivery of the filling yarns being given by theformula:

N metric number of this same yarn when knitting,

R shrinkage of the chain-stitch yarn relative to the filling yarns, thatis to say, the complement to unity of difference between the shrinkageof the stitch forming yarn and of the filling yarn, and

M=number of stitches required per unit of shrunk fabric length.

References Cited by the Examiner UNITED STATES PATENTS 5 FOREIGN PATENTS455,574 3/1949 Canada. 1,242,314 8/1960 France.

565,580 11/1944 Great Britain.

MERVIN STEIN, Primary Examiner. ROBERT R. MACKEY, Examiner.

R. FELDBAUM, Assistant Examiner.

1. A METHOD OF PRODUCING KNITTED FABRICS HAVING A REPETITIVE PATTERN ANDHAVING THE APPEARANCE AND PROPERTIES OF WOVEN FABRICS, COMPRISINGFEEDING A FIRST YARN WHICH CAN BE SHRUNK AND WHICH CAN BE SET AFTERBEING SHRUNK AND FORMING ROWS OF STITCHES THEREFROM, ASSEMBLING SAIDROWS OF STITCHES BY MEANS OF TWO YARNS WHICH ACT AS WEFT YARNS AND JOINAT LEAST TWO ROWS OF STITCHES, FEEDING STRAIGHT YARN, WHICH SHRINKS LESSTHAN THE FIRST YARN AND INSERTING SUCH STRAIGHT YARN IN UNKNITTEDCONDITION BETWEEN THE ROWS OF STITCHES, CONTROLLING THE RATE OF FEEDINGOF THE FIRST YARN RELATIVE TO THE RATE OF FEEDING OF THE STRAIGHT YARNSO THAT THE FIRST YARN HAS A LENGTH WHICH MARKEDLY EXCEEDS THE LENGTH OFTHE STRAIGHT YARN AND WHICH IS SUBSTANTIALLY EQUAL TO THE THEORETICALLENGTH OF THE FIRST YARN WHICH IS REQUIRED TO OBTAIN AN INEXTENSIBLE ROWOF STITCHES AFTER THE SHRINKAGE TREATMENT, SUBJECTING SAID FABRIC TO ASHRINKAGE TREATMENT, AND DURING THE SHRINKAGE TREATMENT MAINTAINING THELENGTH OF THE FABRIC SUBSTANTIALLY EQUAL TO THE LENGTH OF THE STRAIGHTFILLING YARN AFTER ALLOWING FOR ANY SHRINKAGE OF THE FILLING YARN.